Oil & Gas Geology ›› 2009, Vol. 30 ›› Issue (1): 11-16,25.doi: 10.11743/ogg20090102

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Two pooling patterns of superimposed reservoirs in Sebei-1 gas field,the eastern Qaidam Basin

Cheng Fuqi1,2, Jin Qiang2, Zhou Tingquan1, Zhang Shuichang3, Ma Fengliang4   

  1. 1. Research Institute of Geological Sciences, SINOPEC Shengli Oilfield Company, Dongying, Shandong 257015, China;
    2. China University of Petroleum, Dongying, Shandong 257061, China;
    3. PetroChina Exploration & Development Research Institute, Beijing 100083, China;
    4. Northwest Branch of PetroChina Exploration & Development Research Institute, Lanzhou, Gansu 730020, China
  • Received:2008-12-15 Online:2009-02-25 Published:2012-01-16

Abstract:

The Sebei-1 field consists of seven vertically superimposed gas reservoirs with various biogas enrichments.These reservoirs are divided into high-enrichment reservoirs(HER) and low-enrichment reservoirs(LER) based on such data as reserves per unit volume,abundance of gas reserves,and flow rate tested.The pooling conditions for these two types of reservoirs are compared and analyzed.The results are used to define the controlling factors for the biogas enrichment in the field.The lower four deeper reservoirs with burial depth greater than 950 meters are the HER type,while the upper three shallow ones belong to the LER type.The former ones are favorable for gas pooling and enrichment as they are located in the central of a gas-generation zone with biogas charging both from the local area and central depression,and apart from that,they also have favorable re-servoir-seal assemblage,trapping and preservation conditions.In contrast,the later ones are unfavorable for gas pooling and enrichment as the source rocks have not reached peak gas generation,the biogas are mainly sourced from the lower gas reservoirs through diffusion,and the preservation conditions are relatively poor.Based on the analysis of pooling conditions,the paper suggests that the pooling patterns for the HER and LER reservoirs be described as source-charged and dispersion-charged respectively.

Key words: high-enrichment reservoir, low-enrichment reservoir, pooling condition, pooling pattern, Sebei-1 gas field, eastern Qaidam Basin

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